VANCOUVER, B.C.—After last week's scoreless first-leg draw between the Portland Timbers and the Vancouver Whitecaps, it was tough to tell who held the advantage heading into Sunday's Audi 2015 MLS Cup Playoffs Western Conference Semifinal second leg in Vancouver. As it turned out, the Whitecaps' failure to grab an away goal at Providence Park proved costly.

In Sunday's match at BC Place, once Portland's Fanendo Adi struck the crucial away goal for Portland, the Whitecaps were forced to score two to survive the aggregate-goal series. But they couldn't even get one.

Timbers midfielder Diego Chara added a second four minutes into second-half stoppage time as Portland ran out 2-0 winners on the night and on aggregate, moving on to their second Western Conference Championship in three years. They challenge FC Dallas in the first leg at Providence Park on November 22 (7:30 pm ET, FS1 and FOX Deportes in USA; TSN2 in Canada).

Both teams were in attack mode from the kickoff, with Vancouver pushing hard for the early breakthrough in a breathtakingly fast-paced start.

Vancouver's Kekuta Manneh flashed a shot just past the right post six minutes in and he came even closer three minutes later, crashing a low drive off the left post and off the back of goalkeeper Adam Kwarasey for a corner.

Portland created chances on the counter and Diego Valeri curled one wide from distance in the 14th minute.

The 'Caps chances in the series were dealt a serious blow midway through the first half when Manneh rolled his ankle, limping off in the 25th minute to be replaced by veteran Mauro Rosales.

Not for the first time this season, Vancouver's early dominance produced no end results, and after withstanding intense pressure, Portland took control of the series with Adi's opening goal in the 31st minute. The striker buried a Valeri cutback from the end line high into the Whitecaps' net.

Vancouver tried to regroup and 'Caps forward Octavio Riviero came close to leveling in the 44th minute, with a looping header from a Rosales free kick that Kwarasey had to tip over his crossbar.

The second half played out in similar fashion, with Vancouver trying to initiate their attack and Portland looking comfortable in possession.

And aside from a penalty shout from the Whitecaps early in the second half, it was half chances for both teams, and not many of those.

Whitecaps goalkeeper David Ousted had little to do all evening, aside from removing the ball from his own net, though he had to react quickly in the 81st minute, as a Portland free kick came in untouched.

Vancouver seemed resigned to their fate, one sealed four minutes into stoppage time. A quick Portland counterattack saw Chara tuck away a pass to double the Timbers' lead, ensuring they'd advance to a date with FC Dallas.

Armchair Analyst's Take

If you can’t score, you won’t win. And the Vancouver Whitecaps pretty much can not score right now, which is why their season is over.

How bad is it? They’ve been shut out in five of their last six across all competitions, and seven of their last 10. They’ve scored multiple goals just once in the last two months. The only forward on the roster who’s scored since early September is Robert Earnshaw, and he’s not the guy who’s going to win you a playoff series at this stage in his career.

Rivero, Morales, Techera and Rosales have provided zero. Mattocks was invisible. #WhitecapsFC still missing that big game player.

As for the Timbers… it seems like they’ve found their big-game player. Darlington Nagbe has been getting the press and Diego Valeri is rightfully considered one of the league’s most inventive players, but it all runs through Adi at this point in time. He is dictating where the game is played with his ability to hold the ball up and make plays.

And because of that Portland are into their second Western Conference championship in three years.